The water boiler employed in the related art has used gases or petroleum as its fuel, the combustion heat of which heats civil water. This water boiler is advantageous in its quick heating, but has problems that the fuel such as gases or petroleum so that its supply is essential, that the exhaust gas after the combustion is released to contaminate the atmosphere, that an instability is always incorporated by the combustion, and that the combustion makes noises. Especially in the wholly electrified house or condominium increasing year by year and using the electricity for all energy sources, there is no way of supplying the fuel. It is, therefore, the current practice that the case, in which the water boiler cannot be used, is increasing.
Thus, there has been developed a heat pump water boiler of a reservation type provided with a hot-water reserving tank. This heat pump water boiler gradually comes into wide use, because it can solve the problems of the combustion type water boiler and because it has advantages that the water boiler can be easily installed without any new infrastructure in the wholly electrified house or condominium, that the water boiler is of the heat pump type and has a high heat efficiency to keep a capacity of three times or more to the input, and that the water boiler is enabled to reserve hot water in a reservoir tank by using the inexpensive late-night electric power for the run, thereby to lower the running cost.
From the housing problems of recent years, however, more and more demanders have to despair of the installation of the heat pump water boiler because of lack of installation space.
For those demanders, there has also been developed a water boiler, which can be installed in a narrow space because the heat pump unit and the hot-water reserving tank unit are integrated.
This water boiler is exemplified by the heat pump water boiler (RHK-23BAV of Hitachi), as disclosed in Non-Patent Document 1.
FIG. 4 is a circuit configuration diagram of such heat pump water boiler, and FIG. 5 is a schematic configuration diagram of the heat pump water boiler shown in FIG. 4.
The heat pump water boiler shown in FIG. 4 comprises: a refrigerant cycle constituted to include compressors 120 and 121, water-refrigerant heat exchangers 122 and 123, pressure reducing valves 124 and 125, evaporators 126 and 127 and blowers 128 and 129; and a hot-water supplying cycle including a hot-water reserving tank 130, a mixing valve 131, a solenoid valve 132, a hot-water supplying circulation water pump 133 and a bath warming/heating circulation water pump 134 connected through pipes. The hot water is generated in the refrigerant cycle and is directly supplied to a faucet 135 and a bath tab 136, and reserved hot water is supplied from the hot-water circuit. Moreover, this heat pump water boiler is constituted into an integral type housing the refrigerant cycle and the hot-water supplying cycle wholly in one unit, as shown in FIG. 5.
In a heat pump water boiler disclosed in Patent Document 1, on the other hand, the refrigerant unit is arranged over the hot-water reserving unit so that the constitution can be installed in a narrow space.
FIG. 6 is a schematic configuration diagram of such heat pump water boiler.
Non-Patent Document 1: Refrigeration, Edition of March, 2004, Vol. 29, No. 917, pgs. 23-28
Patent Document 1: JP-A-58-158448